Ribbon-feed mechanism



Nov. 1942. L. s. WILLIAMS RIBBON-FEED MECHANISM 4 Sheets-Sheet l FilgdJuly 25. 1941 Lqwrence 5. W/W/ams INVENTOR ATTORNEYS Nov. 3, 1942. 7L.s. WILLIAMS 2,300,755

RIBBON-FEED MECHANISM Filed July 25, 1941 4 Shee ts-Sheet 2 Lawrence J.-Mfl/ams INVENTOR I ATTORNEYS Nov. 3, 1942.

L. s. WILLIAMS RIBBON-FEED MECHANISM 4 Sheet-Sheet 3 Filed Jugy 25, 19412 a 4 3 9 n 79 v i 6 J 9 E: 0 Z 3 6w m y TV H: m a I Q Lawrence J.M/////am3 INVENTOR ATTORNEYS L. s. WILLIAMS ,300,755 RIBBON-FEEDMECHANISM 'Nov. 3, 1942.

Filed July 25, 1941 4 Sheets-Sheet 4 I I LaW/"en'ce 5. [MW/007s E 1INVENTOR zmwmfi Patented Nov. 3, 1942 l 2,300,755 RIBBON -FEED MECHANISMLawrence S. Williams, Toledo, Ohio, assignor to Toledo Scale Company,Toledo, Ohio, a corporation of New Jersey Application July 25, 1941,Serial N0. 404,051

12 Claims. (Cl. 101-436) This invention relates to ribbon-feedmechanisms of the type which automatically reverse the direction of feedof the ribbon when it has been fed past the printing mechanism forsubstantially its full length, and more particularly to means foreffecting such reversal of feeding direction.

Most ribbon-reversing mechanisms are constructed so that the directionof feed of the ribbon is changed by moving a feeding pawl, or a pair offeeding pawls, out of engagement with one ribbon spool and intoengagement with the other at the time the reversal of direction of feedis desired.

The bodily shifting of the feeding pawl, or pawls, has a seriousdisadvantage if a mechanism operated in this way is to be used with anydevice which applies pressure to the ribbon, and the medium which is toreceive the impression, from both sides. In a device of this type, theribbon is held stationary at the moment of impression. If the feedingpawl shifts to the other spool and attempts to feed the ribbon duringthe impression, the ribbon is very likely to be torn. If this isprevented by having the ribbon less tightly held, then movement of theribbon will cause a smeared impression. Since the ribbon is usually fedduring the same cycle as when the impression is taken, the timing of thefeeding and the impression taking must be very carefully adjusted toprevent either one of these two undesirable results.

Further diificulties arise in most ribbon-reversing mechanismsdue to theemployment of a toggle-type over-center device to move the pawl from onespool to another and to hold it in engagement. Over-center devices ofthis type compress a spring as they approach dead center and must becarried past dead center by the force created by the shifting deviceoperated by the ribbon so that the extension of the spring can beemployed to shift the feeding pawls to change the direction of feed ofthe ribbon. If any friction exists in such an over-center device, sinceit is pulled only to dead center, it may very easily remain there andthe mechanism will fail to feed in either direction. This failure tochange over properly is the cause of most of the trouble encountered inribbon feeding mechanisms using over-center devices to bodily move thefeeding pawls from one ribbon spool to the other.

One type of ribbon-reversing mechanism often used is the so-called bulktype in which a rider wound on a spool and which rider, being pivoted,is swung away from the center of the spool by the increase in the bulkof the ribbon being accumulated on the spool. As the rider is swung awayfrom the center of the spool, the toggle member is moved toward deadcenter, and when a sufficient bulk has accumulated on the spool, shouldsnap over to the other side of center.

Operation, however, is often far from satisfactory, since the frictionmentioned above may be aggravated by disadvantages peculiar to the bulktype of mechanism which include the softening of the mass of the ribbonas it winds on the spool and the wasting of some of the feeding strokeand the built-up tension in the irregularities and unevenness inthesubsequent feeding.

This unevenness of tension is particularly undesirable-where a reversingmechanism employing a toggle-like spring-actuated over-center device isused.

To overcome some of the disadvantages of the bulk type of mechanism,there is sometimes used the so-called eyelet type of mechanism.

In this device a small eyelet, clipped into the ribbon near its end,actuates the reversing mechanism as, or shortly after, it leaves theunwinding spool. As in the bulk type, though, if the usualspring-actuated toggle-like over-centerdevice is used, the ribbontension must compress the spring in the toggle and, if friction exists,it may easily stick at dead center.

To eliminate some of these difficulties, mechanisms have been designedwhich areoperated in one direction only and which, when moving forward,coil a spring, the tension of which will return the ribbon after it hasbeen fed its full length in one direction. This, however, causes rapiddeterioration of the ribbon because of the high speed of return when thecoiled spring'is released and so shortens the ribbon life as to make thetotal result less desirable than with the reversing type of feedingmechanism.

Because of these many diffic'ulties encountered is pressed against thesurface of the ribbon being in the construction of ribbon-feedingandribbonreversing mechanisms, the usual one is quite complicated,subject to mechanical failure, uneven in operation and will not worksatisfactorily where the feeding stroke and the return stroke of thefeeding pawls are not substantially harmonic. Since many devices,incorporating ribbon-feeding and reversing mechanisms, do not have evenfeeding and returning strokes, the use of such mechanisms in suchdevices has been relatively unsatisfactory.

It is an object of this invention to provide a ribbon feeding andreversing mechanism, the operation of which is positive and which willnot interfere with the necessity for holding the ribbon during aprintingcycle.

It is another object of this invention to provide a ribbon feeding andreversing mechanism which will not move the ribbon during-the time thatan impression is being taken from it and will thus neither tear theribbon nor smear the impression.

Another object of this i vention is to provide a ribbon mechanism whichis relatively simple in construction and yet durable and not liable toget out of adjustment.

It is still another object of this invention to provide a ribbonmechanism which is fed in both directions by means of a pawl but whichdoes not bodily move the pawl to change the direction of feeding.

It is yet another object of this invention to provide a ribbonfeedingand reversing mechanism which changes the direction of feed ofthe ribbon by changing the path through which the feeding pawl maymoverather than by changing the position of the feedin pawl itself andits subsequent motion. 7

It is still another object of this invention to provide an over-centerdevice for changing the direction of feed of a ribbon mechanism which isactuated by the ribbon itself and held on one side or the other ofcenter by magnetic means.

It is a more specific object of this invention to provide a magneticallydetained over-center device for varying the path of movement of afeeding pawl to reverse the direction of feed of a ribbon mechanism.

Another more specific object of this invention is to provide a ribbonmechanism which can be used in connection with a printing disk and isadapted to feed the ribbon before the disk, the impression receivingmedium and the ribbon are squeezed together to make an impression.

More specific objects and advantages are apparent from the description,in which reference is had to the accompanying drawings illustrating apreferred form of ribbon feed mechanism embodying the invention.

In the drawings:

Fig. I is a front elevation of a preferred embodiment of the inventionas shown in connection with the type carrying wheel of a printing scale.

Fig. II is a View in vertical section on a larger scale, taken from theleft side of the mechanism illustrated in Fig. I. n

Fig. III is a plan View on an enlarged scale of a ribbon mechanismembodying the invention.

Fig. IV is a vertical sectional view, taken on the line IV-IV of Fig.III.

Fig. V is a fragmentary vertical sectional View, taken on the line VV ofFig. III.

ing the mechanism in a different position in its operating cycle.

Fig. VIII is an enlarged fragmentary View in perspective of a portion ofthe mechanism illustrated in Fig. III.

Fig. IX is a schematic wiring diagram of a printing scale embodying theinvention as illustrated in Fig. I.

These specific drawings and the specific description that follows merelydisclose and illustrate the invention and are not intended to imposelimitations upon the claims.

Mounted within a dial housing Ill (Fig. II), on a subframe I I, is anindicator shaft I2 having an indicator [3 attached to one end. Fixed onthe shaft 12 is a pinion M, which is driven by a rack 15 attached to theload counterbalancing mechanism .(not shown). The indicator l3 sweepsover a dial IE to indicate the weights placed upon Fig. V1 is a stillfurther enlarged fragmentary i Fig-VII is a view similar to Figure VI,show 75 the scale. Attached to the opposite end of the shaft [2, fromthe indicator I3, is a type bearing disk l1.

Mounted on a bracket [8 and supported bya secondary bracket l9, attachedto the housing It (Fig. II), is a solenoid housin 20. A verticallymovable core rod 2| is located within a solenoid 22 in the housing 26.The upper end of the core rod 2| has attached thereto a cross head 23.Pivoted on the cross head 23 are links 24 and 25. The links 24 arepivoted in a lower portion 26 of a horizontally slidable abutment 21(Fig. IV). The abutment 2! slides on rods 28, which are fastened in thesecondary bracket I9. A bearing ball 28a is held in the upper end of asupport stud 29, which is screwed into the top of the solenoid housing20, and serves to support the rear of the abutment 21. The link issimilarly pivoted in the lower portion of a horizontally slidable platen30.

When the solenoid 22 is energized, the core rod 2| is thrust upwardlypushing outwardly on the lower portions of the opposed abutment 27 andplaten 30 and moving an inner face SI of the abutment 21 and an innerface 32, of the platen 30 towards each other.

The lower edge of the type bearing disk ll extends downwardly betweenthe opposedgfaces 3i and 32 of the abutment 21 and the platen 39. Alsointerposed between the faces 3| and 32, and adjacent the periphery ofthe disk ll, is a metallic strip 33 bearing a character in the form of apointer which is positioned to indicate the weight on the scale bypointing to the figure printed from the disk II.

The vertical portion of a ribbon mechanism support plate 34 is fastenedto the platen 3E] and the plate has a horizontal shelf-like portionextending backward from the platen 30. A U shaped support member 35(Fig. V) is resiliently attached, by means of a spring encircled bolt36, to the vertical portion of the support plate 34 at one side ofplaten 30. A similar'U shaped supporting member 31 is mounted on theopposite end of the support plate 34. Metallic guides 38 are supportedby the other arm of the U shaped supporting members 35 and 3'! and.extend between the platen 30 and printing disk I1 (Fig. IV). U clips 39(Figures III and V) are fastened to the support plate 35 and have onebifurcated arm in the legs of which th U shaped support members 35 and31 are horizontally slidable. The center of the metallic guides 38, thatis those portions actually passing between the printing surfaces of theabutment-2'1 and platen 30, have apertures therein to permit the platen39 to force a card 49 (Fig. II) or other impression receiving substance,into contact with a ribbon 4| also passing through the guides 38 andthus to print an impression ofthe type on the disk I! on the surface ofthe card. I

In order to secure a firm impression of the type on the disk 11, theabutment 21 and platen 39 are brought firmly towards each other. Sincethe guides 38 must be kept in relatively the same position to receivethe card 49, andshould not move back and forth with the platen 39,because such movement would bend or crease the card, their connectionthrough the U shaped support members 35 and 31 to thesupport plate 34,and thus to the platen 39, is through the spring encircled bolts 36which, being resilient, permits movement on the part of the supportplate 34 and still holds the guides as in position. The

clips 39 prevent any sagging of this resilient connection.

The ribbon 41 passes around out-rigger spools 42, and thence to ribbonfeeding spools 43 and 44. The spools 43 and 44 are rotatable uponvertical axles 45 which are fastenedon the support plate 34. Springs 46are chpped in the support plate 34 and pass around the peripheries ofthe spools 43 or 44. These springs 45 serve as tension brakes on thespools 43 and 44 to prevent back lash of the ribbon 4 l Also mounted onthe axles 45, of spools 43 and 44, are ratchet wheels I 41 and 48respectively.

A U shaped driving pawl 49 (Fig. IV) has one arm mounted in a bushing.59, which is slidable in a slot 51 in the support plate 34. The samearm of the pawl 49 passes through a clip 52, which is attached to theabutment 21 and which is adapted to slide the pawl 49 in the bushing 55in a direction opposite to the movement of the platen 39 and the supportplate 34. The lower portion of the pawl 49 is attached, by means of aspring 53, to a stud 54 attached to the underside or" the support plate34. The other arm of the pawl 49 has a sharpened edge 55 extending partway up its length and a flattened portion 56 extending above the levelof the support plate 34. The edges of the flattened portion 59 areadapted to engage the teeth of either the ratchet wheel 4! or theratchet wheel 48. j a

A toggle member 51 is pivotally mounted on a finger 58, which extendsupwardly through the support plate 34. A walking arm 59 (Figures III,

VIII) is mounted upon the arms of a vertical staple E0, the body ofwhich passes through a horizontal hole 6| bored transversely through thetoggle member 51. The walking arm 59 has upturned bifurcated endsthrough which the ribbon 4| passes. Mounted in small brackets 52; one oneach side of the forward end of the toggle member 57 and with theirfaces in vertical planes converging on the pivot finger 58 of the togglemember 51, are small horseshoe magnets 63;

The end of the toggle member 57, which is opposite to that extendingbetween the magnet 63, has mounted therein a downwardly extending stud64, the forward edge of which is knifeshaped and opposed to the sharpedge of the pawl 49 (Fig. IV). Pivoted on a stud 65, which extendsdownwardl from the support plate 34, is a horizontally disposed guidingplate 65 (Figures IV and VI). The guiding plate 66 has an open centerthrough which the arm of the pawl 49 extends which has the sharp edge 55and the flattened surface 55. The guiding plate 66 has a in front of thespear point projection'tl. Pivotally mounted on the'guiding plate 63 areback pawls 68 and 69, which engage the ratchet wheels 41 and 48respectively to prevent their being turned in the wrong direction.Springs 19 hold the back pawls 68 and 69 against the teeth of theratchet wheels 41,-and 48-andagainst" limit studs H which projectupwardlyfrom the guid ing plate 65. I

The lower end of thesolenoid core rod 2| II) has attached thereto aplate 12 and is surrounded by a spring 1 3 which,--'when the core rod ismoved upwardly, upon energization of the solenoid 22, is compressedbetween the plate 12 and the solenoid housing 20.- When; the solenoid isde-energized, the spring 13 serves to return thesolenoid core'rod to itslower position. A vertical switch (actuating rod 14 is attached to thelower end of the core rod 2| and extends downwardly through aswitchcontact 15'. The contact 75 is closed when the solenoidcore rod 2lapproaches the limit of its upward stroke and is opened shortly after ithas startedits return stroke.

In Figure IX, there is shown a wiring diagram of a printing scaleembodying the invention;-

the solenoid operated contact 15.' Theopposite' side of thesolenoid'ioperated Contact 151s connected to one side of a.normally'open contact 82' and through a resistance 83 to one side ofiarelay coil 84, the other side of which is connected tothe lead 18. Thepush button 89 is' also connected to one side of the normally opencontact 82 and through a normally closed contact 85, protected by acondenser '85, through a lead 87, to the other side of therectifier 19.7

he operation of the ribbon feedinga'nd'ree versing meohanism, as usedfinconnection with the printing scale illustrated in Figure I', will now bedescribed. When the printing diskli has come to rest with the propertype character positioned over the platen 39, the operator closes thepush button switch lw. .Current flows from the line through the switch80, the normally closed contact to the rectifier I9 and thenito thesolenoid 22. The solenoid core rod 2! (Fig. II) .is moved upwardlywhich, through the connections" on the cross head 23, moves the'faces ofthe platen'39 and the abutment 21 towards each other by means of thelinks 24 and 25. A card or slip 45, having been inserted between theplaten'35 and. the printing disk [1, receives an impression of the ingtype on the strip 33.

type on the disk i! positioned above the indicate.

Atthe same time, the movement of theiabut' ment 2! towards the rear ofthe mechanism has moved the clip 52, and through it, the pawl 49.

In Fig. VI, the mechanism .is shown with the. pawl 49 in the positionwhich-it would ocoupyu just after the beginning of the upward stroke of.

the solenoid core rod 2!. The ribbon 4| is almost I entirely unwoundfrom the ribbon spool '43 and an eyelet 88, clipped into the ribbon 4|near its end, has almost reached the end of the walking arm 59throughwhiohthe ribbon ilpasses. The toggle member 51 is still locatedin" the downwardly extending stud 64, vmounted in' the toggle member 51,is positioned above andslightly From' the push position which itoccupies when the ribbon mechanism is feeding onto the spool 44.Thus-the knife edge stud 64 is positioned above and slightly to the leftof the spear point projection 61 on the guiding plate 66. Theguiding-plate 66 is positioned normally with the point of the spearpoint projection 61 directly on the center line of travel of the pawl49. As the pawl 49 is moved towards the rear, the knife edge 55, in itsupturned end, approaches the point of the spear point projection 6'! butis guided to one side or the other of the spear point projection 61- bythe knife edge stud 64 which depends from the toggle member 51. Thetoggle member 5! is, of course, positioned either to oneside or theother of the spear point projection 6'1 by being retained against one orthe other of the magnets 63. As the knife edge 55 of the pawl 49 strikesthe sides of the knife edge stud 64, it is guided to one side of thespear point projection 61. In Fig. VI, subsequent movement of the pawlwill bring the two knife edges toward each other and their slantingfaces will guide the pawl 49 to theright of the spear point projection61. Since the clearance between the vertical edges of the spear pointprojection 6! and the teeth of the ratchet wheel 48 is not sufficient topermit the entry of the arm of the pawl 49, one edge of the flat portion56 engages a tooth on the ratchet wheel 48 and the opposite edge acts asa cam to pivot the guiding plate 66 in a clockwise direction (Fig. VII).The pivoting of the plate 66 swings the limit stud H, fastened thereto,which disengages the back pawl 68 from the teeth of the ratchet wheel 41to permit counterclockwise rotation of the ribbon spool 43 to allow theribbon to be unwound from that spool. The pawl 49 has now approached thelimit of its rearward stroke, and the spool 44 has wound on anadditional amount of the ribbon 4|.

The back pawl, engaged in the teeth of the ratchet wheel 48, is snappedup by the teeth of the wheel 48 to permit the spool 44 to rotate in acounter-clockwise direction and wind on the ribbon.

The solenoid core rod 21 (Fig. IX), now having reached the upward limitof its stroke, closes the contact 15, which energizes the relay coil 84,and closes the normally open contact 82 and opens the normally closedcontact 85. The circuit through the rectifier I9 is now open and thecore rod 2| begins to descend. The resilient construction of theconnection between the core rod 2| and the switch 15 holds the switch 15closed for a short time during descent. Thus current passes through thesolenoid coil 84 for a sufli I ciently additional length of time toprevent the switch 85 from reclosing until the operator releases thebutton 88 which he should do immediately upon the printing of theweight. If, however, the operator should fail to release the push button89, current will continue to flow through the coil 84, the contact 82and the push button 80, thus holding the contact 82 closed even afterthe contact 15 has been broken and preventing the contact 85 fromclosing which would start a second printing cycle. This is a safetycircuit which prevents the repetition of printing cycles, no matter howlong the button 88 is held closed. If the push button 88 is nowreleased, the coil 84 is de-energized, the contact 82 snaps open and thecontact 85 is closed to prepare the circuit for a subsequent printingoperation.

When the solenoid core rod 2| starts its descending stroke, the platen39 andthe abutment 21 are moved back to theiroriginal positions.

Thepawl 49, through'its connecting clip 52, is also returned to itsoriginal position. The guiding plate 66, under tension of the spring 10connected to the back pawl 69 and working against the ratchet wheel 48,is swung in a counterclockwise direction back to the center positionshown in Fig. VI.

If the feeding of the ribbon in the feeding stroke is suflicient to'bring'the eyelet 88 into contact with the end of the walking arm 59(the next stroke after that illustrated in Figures VI and VII), thetension on the ribbon 4| will pull the walking arm 59 bodily to theleft. This movement, through the staple 60, will pivot the toggle member51 on the finger 58 which will swing its forward end away from that oneof the magnets 63, against which it is being held, and far enoughtowards'the other magnet 63 for the magnetic force to seize it and pullit against the other magnet 63. The toggle member 51 will thus berotated in a counterclockwise direction on the finger 58 and positionedagainst the other magnet 63 than that against which it is shownpositioned in Figures VI and VII. This will swing the knife edge stud 64to the right (Fig. VI) and in subsequent strokes of the pawl 49, itsedge 55 and flat portion 56 will travel on the lefthand side of thespear point projection 61 engaging the teeth in the ratchet wheel 41 tofeed the ribbon on the spool 43 and in the opposite direction from thatin which it is fed in the stroke illustrated in Figures VI and VII. Thecycle of feeding will now be exactly the same as that described but theflat portion 56 of the pawl 49 will be moved through a different path.

Thus the reversing movement of the ribbon mechanism does not bodily movethe pawl 49 out of engagement with one ribbon spool and into engagementwith another, but rather changes the path through which the latchingedge of the flat portion 56 of the pawl 49 moves to cause the pawl toengage the other ribbon spool and does not change the direction ofstroke of the pawl actuating members. It is impossible for the togglemember 51 to be. moved to dead center and left there since if it weremoved to dead center only a very slight force would be needed to breakthe balance between the magnetic pull of the two magnets 63 and suchslight contact is always afforded on the return stroke of the pawl 49and the return rocking motion of the guiding plate 66.

The embodiment of the invention that has been disclosed may be modifiedto meet various requirements.

Having described the invention, I claim:

1. In a ribbon feeding and reversing mechanism, in combination, aribbon, a pair of alternately drivable spools on which said ribbon isadapted to be wound, spool driving mechanism, means for shifting saidspool driving mechanism from driving relation with one of said spools todriving relation with the other of said spools and magnetic means forretaining said spool driving mechanism in driving relation with one ofsaid spools until moved by said shifting means into driving relationwith the second of said spools, said magnetic means then retaining saidspool driving mechanism in driving relation with the second of saidspools.

2. In a ribbon feeding and reversing mechanism, in combination, aribbon, a pair of spools on each of which said ribbon is adapted to bewound, spool driving mechanism, means for conditioning said spooldriving mechanism for driving oneof said spools, magnetic means forretaining said mechanism in condition to drive such spool and meansoperable when a definite portion of said ribbon is wound on'suchspoolfor causing said conditioningmeans .to condition said mechanism fordriving the second of said spools, said magnetic means then operatingfor retaining said mechanism in condition to drive the second of saidspools. V

3. In a ribbon feeding and reversing mechanism, in combination, aribbon, a pair of spools on each of which said ribbon is adapted to bewound, spool driving mechanism, means for conditioning said spooldriving mechanism for driving one of said spools, magnetic means forretaining said mechanism in condition to drive such spool and ribbonactuated shifting means for shifting said conditioning means tocondition said mechanism for driving the second of said spools, saidmagnetic means then operating for retaining said mechanism in conditionto drive the second of said spools.

4. In a ribbon feeding and reversing mechanism, in combination, aribbon, a pair of spools on each of which said ribbon is adapted to bewound, spool driving mechanism, means for conditioning said spooldriving mechanism for driving one of said spools, magnetic means forretaining said mechanism in condition to drive such spool and ribbonactuated shifting means operable when a predetermined amount of saidribbon is wound on such spool for shifting said conditioning means tocondition said mechanism for driving the second of said spools, saidmagnetic means then operating for retaining said mechanism in conditionto drive the second of said spools.

5. In a ribbon feeding and reversing mechanism, in combination, aribbon, a pair of spools on each of which said ribbon is adapted to bewound, spool driving mechanism, alternately positionable guiding meansfor deflecting said driving mechanism into one of two paths, eachleading to engagement with a different one of said spools and meansoperable when a definite portion of said ribbon is wound on such spoolfor moving said alternately positionable guiding means from one of itsalternate positions to the other.

6. In a ribbon feeding and reversing mechanism, in combination, aribbon, a pair of alternately drivable spools on which said ribbon isadapted to be wound, means for driving said spools, alternatelypositionable guiding means for guiding said driving means through eitherof two paths, each leading to engagement with a different one of saiddrivable spools, ribbon actuated means for shifting said guiding meansand magnetic means for retaining said guiding means in one of itsalternate positions until moved to the other by said ribbon actuatedshifting means.

7. In a ribbon feeding and reversing mechanism, in combination, aribbon, a pair of spools on each of which said ribbon is adapted to bewound, spool driving mechanism, alternately positionable guiding meansfor deflecting said driving mechanism from its path of movement througheither of two alternate paths, each leading to engagement with adifferent one of said spools, means operable when a definite portion ofsaid ribbon is wound on such spool for moving said alternatelypositionable guiding means from one of its alternate positions to theother and an over-center device for retaining said alternatelypositionable guiding means in either of its positions until moved to theother by said means operable when a definite portion of said ribbon iswound on such spooL- v 8,. 'Ina ribbon feeding and reversing mecha-.nism, in combination, a ribbon, a pair ofv spools on each of which saidribbon its adapted to be wound, spool driving mechanism, meansfor-conditioning saidspool driving mechanism forld'ri'v- 'ingone of saidspools, a magnet for retaining said mechanism in condition to drive suchspool,

actuating means operable when a definite portion of said ribbon is woundon such spool for causing said conditioning means to condition saidmechanism for driving the second of said spools and a second magnet forretaining said mechanism in condition to drive such second spool, saidfirst and second magnets in association with said conditioning meansforming an over-center device for controlling said actuating means andsaid conditioning means.

9. In a ribbon feeding and reversing mechanism, in combination, aribbon, a pair of spools on each of which said ribbon is adapted to bewound, spool driving mechanism, an alternately positionable guidingmember adapted to be positioned to guide said spool driving mechanisminto engagement with one or the other of said spools, ribbon actuatedmeans for positioning said guiding member, and magnetic means forretaining said guiding member in one of its positions until moved to theother by said ribbon actuated means, said magnetic means then retainingsaid guiding member in the other of its positions.

10. In a ribbon feeding and reversing mechanism, in combination, aribbon, a pair of spools on each of which said ribbon is adapted to bewound, spool driving mechanism, a guiding member having alternatepathways through which said mechanism is adapted to be moved, each ofsaid pathways leading said mechanism to operative engagement with adifferent one of said spools, ribbon actuated means for conditioningsaid spool driving mechanism to follow one or the other of said pathsand magnetic means for retaining said ribbon actuated means in positionto condition said mechanism to drive one of said spools until saidribbon actuated means is moved to the other of their positions, saidmagnetic means then retaining said ribbon actuated means in its otherposition.

11. In a ribbon feeding and reversing mechanism, in combination, aribbon, a pair of spools on each of which said ribbon is adapted to bewound, a spool driving pawl having a knife edge and a driving edge, analternately positionable guiding bar having a knife edge adapted to bemoved from one side to the other of the line of movement of the knifeedge of said driving pawl whereby when said guiding arm is in one of itsalternate positions such knife edges will guide said pawl through onepath of movement and lead such driving edge into engagement with one ofsaid spools and when said arm is in the other position such knife edgeswill guide said pawl through a second path of movement and lead suchdriving edge into engagement with the second of said spools and meansfor shifting the position of said guiding bar when a specified amount ofribbon is wound on such spool.

12. In a ribbon feeding and reversing mechanism, in combination, aribbon, a pair of spools on each of which said ribbon isadapted to bewound, a spool driving pawl having a knife edge and a driving edge, analternately positionable guiding bar having a knife eds adapted to bemoved from one side to the other 01 the line of movement of the knifeedge of said driving pawl whereby when said guiding arm is in one of itsalternate positions such knife edges will guide 5 said pawl through onepath of movement and lead such driving edge into engagement with one ofsaid spools and when said arm is in the other position suchknife edgeswill guide said pawl through a second path of movement and lead 10 suchdrivin edge into engagement with the sec-- ond of said spools, means forshifting the position of said guiding bar when a specified amount ofribbon is wound on such spool and. magnetic meansfor retaining saidguiding bar in one of, its positions until moved by said shifting meansto its other position, said magnetic means then retaining said guide barin its second position until reshifted by said shifting means.

LAWRENCE S. WILLIAMS.

